Appendix III Land Cover

Appendices

Appendix III

Land Cover
in the
New River Basin

A-III-1
Land Cover

Land cover can be an important way to evaluate the effects of land use changes on water quality.
Unfortunately, the tools and database to do this on a watershed scale are not available. The
information below describes two different ways of presenting land cover in the New River basin.

The state’s Center for Geographic Information and Analysis (CGIA) land cover information is
useful in providing a snapshot of land cover in the basin from 1993 to 1995. This information is
also available in a GIS format so it can be manipulated to present amounts of the different land
covers by subbasin or at the watershed scale. The Natural Resources Inventory (NRI) land cover
information is presented only at a larger scale (8-digit hydrologic unit), but the collection
methods allow for between year comparisons. The two datasets cannot be compared to evaluate
land cover data. This information is presented to provide a picture of the different land covers
and some idea of change in land cover over time. In the future, it is hoped that land cover
information like the GIS formatted dataset will be developed to make more meaningful
assessments of the effects of land use changes on water quality. This dataset would also be
useful in providing reliable and small-scale information on land cover changes that can be used
in water quality monitoring, modeling and restoration efforts.

CGIA Land Cover

The North Carolina Corporate Geographic Database contains land cover information for the New
River basin based on satellite imagery from 1993-1995. CGIA developed 24 categories of
statewide land cover information. For the purposes of this report, those categories have been
condensed into five broader categories as described in the following table. The chart provides an
illustration of the relative amount of land area that falls into each major cover type for the New
River basin.

Land Cover Type Land Cover Description
Urban Greater than 50 percent coverage by synthetic land cover (built-upon area)
and municipal areas.
Cultivated Cropland Areas that are covered by crops that are cultivated in a distinguishable pattern.
Pasture/Managed Herbaceous
Areas used for the production of grass and other forage crops and managed
areas such as golf courses and cemeteries. Also includes upland herbaceous
areas not characteristic of riverine and estuarine environments.
Forest/Wetland Includes salt and freshwater marshes, hardwood swamps, shrublands and
forested areas (i.e., needleleaf evergreens, deciduous hardwoods).
Water Areas of open surface water, areas of exposed rock and areas of sand or silt
adjacent to tidal waters and lakes.

A-III-2

NRI Land Cover Trends

Land cover information in this section is from the most current National Resources Inventory
(NRI), as developed by the Natural Resources Conservation Service (USDA, updated June
2001). The NRI is a statistically based longitudinal survey that has been designed and
implemented to assess conditions and trends of soil, water and related resources on the Nation’s
nonfederal rural lands. The NRI provides results that are nationally and temporally consistent
for four points in time -- 1982, 1987, 1992 and 1997.

In general, NRI protocols and definitions remain fixed for each inventory year. However, part of
the inventory process is that the previously recorded data are carefully reviewed as
determinations are made for the new inventory year. For those cases where a protocol or
definition needs to be modified, all historical data must be edited and reviewed on a point-by-
point basis to make sure that data for all years are consistent and properly calibrated. The
following excerpt from the Summary Report: 1997 National Resources Inventory provides
guidance for use and interpretation of current NRI data:

The 1997 NRI database has been designed for use in detecting significant changes in resource
conditions relative to the years 1982, 1987, 1992 and 1997. All comparisons for two points in
time should be made using the new 1997 NRI database. Comparisons made using data
previously published for the 1982, 1987 or 1992 NRI may provide erroneous results because of
changes in statistical estimation protocols, and because all data collected prior to 1997 were
simultaneously reviewed (edited) as 1997 NRI data were collected.

The following table summarizes acreage and percentage of land cover from the 1997 NRI for the
major watersheds within the basin, as defined by the USGS 8-digit hydrologic units, and
compares the land cover to 1982 land cover. Definitions of the different land cover types are
also presented.

Forest
75%
Cultivated
Cropland
22%
Pasture/Managed
Herbaceous
1%
Urban
1%
Water
1%

A-III-3
MAJOR WATERSHED AREAS
1997 1982
TOTALS TOTALS
Acres % of Acres % of % Change
LAND COVER (1000s) TOTAL (1000s) TOTAL Since 1982
Cult. Crop 6.0 1.2 14.6 3.0 -58.9
Uncult. Crop 9.3 1.9 22.4 4.6 -58.5
Pasture 121.6 25.1 126.9 26.2 -4.2
Forest 267.7 55.2 264.8 54.6 1.1
Urban & Built-Up 31.1 6.4 21.3 4.4 46.0
Federal 8.3 1.7 8.3 1.7 0.0
Other 40.6 8.4 26.3 5.4 54.4
Totals 484.6 99.9 484.6 99.9
% of Total Basin 100.0 100.0
SUBBASINS 05-07-01, 05-07-02, 05-07-03
8-Digit Hydraulic Units 05050001

Type Description
Cultivated Cropland Harvestable crops including row crops, small-grain and hay crops, nursery and orchard
crops, and other specialty crops.
Uncultivated Cropland Summer fallow or other cropland not planted.
Pastureland Includes land that has a vegetative cover of grasses, legumes and/or forbs, regardless of
whether or not it is being grazed by livestock.
Forestland
At least 10 percent stocked (a canopy cover of leaves and branches of 25 percent or
greater) by single-stemmed trees of any size, which will be at least 4 meters at maturity,
and land bearing evidence of natural regeneration of tree cover. The minimum area for
classification of forestland is 1 acre, and the area must be at least 1,000 feet wide.
Urban and
Built-up Areas
Includes airports, playgrounds with permanent structures, cemeteries, public
administration sites, commercial sites, railroad yards, construction sites, residences, golf
courses, sanitary landfills, industrial sites, sewage treatment plants, institutional sites,
water control structure spillways and parking lots. Includes highways, railroads and
other transportation facilities if surrounded by other urban and built-up areas. Tracts of
less than 10 acres that are completely surrounded by urban and built-up lands.
Other
Rural Transportation: Consists of all highways, roads, railroads and associated rights-
of-way outside urban and built-up areas, private roads to farmsteads, logging roads and
other private roads (but not field lanes).
Small Water Areas: Waterbodies less than 40 acres; streams less than 0.5 mile wide.
Census Water: Large waterbodies consisting of lakes and estuaries greater than 40
acres and rivers greater than 0.5 mile in width.
Minor Land: Lands that do not fall into one of the other categories.
Source: USDA, Soil Conservation Service - 1982 and 1997 NRI

A-III-4
Data from 1982 are also provided for a comparison of change over 15 years. During this period,
urban and built-up land cover increased by nearly 10,000 acres (54.4 percent). Uncultivated
cropland and pastureland decreased by over 18,000 acres (58.5 and 4.2 percent, respectively).
Forest cover increased by nearly 3,000 acres (1.1 percent), and cultivated cropland cover
decreased by almost 9,000 acres (58.9 percent). Most land cover change is accounted for in the
areas surrounding the local municipalities in the New River basin. Below is a graph that presents
changes in land cover between 1982 and 1997.

-58.9 -58.5
-4.2
1.1
46.0
0.0
54.4
-80.0
-60.0
-40.0
-20.0
0.0
20.0
40.0
60.0
80.0
Cult. Crop Uncult. Crop Pasture Forest Urban & Built-
Up
Federal Other
Land Cover Type
La
n
d

C
o
v
e
r

C
h
a
n
g
e
s

(
%
)
Source: USDA-NRCS, NRI, updated June 2001